In the manufacture of products and components, various small parts, such as bolts, nuts, washers, screws, and the like, are employed that mainly serve a functional role in the final assembly. In order to prepare these parts for final assembly, a coating material is typically deposited on at least portions of the part to cover the substrate. Of particular importance is the coating of Class A surfaces (i.e. those surfaces that are readily visible in the final assembly when the part is installed), that provide a finished appearance to the part and/or provide protection to the underlying substrate from damaging effects as a result of use, wear, and/or environmental conditions. For example, if the small part is a combination of a bolt and an integral washer, particular attention is directed to depositing a coating on the head of the bolt and the visible portions of the washer.
Because of the substantial number of small parts employed in the manufacturing industry, various coating techniques have been employed for depositing material on these parts at high speeds. In one known prior art coating system, small parts are spread and loosely placed on a large conveyor belt for high-speed coating, particularly electrophoretic coating. While on the conveyor belt, the loosely placed parts are affected by forces from the belt, such as forces due to inertia, vibration, and the like, that allow the individual parts to randomly move on the belt. In many instances, the individual parts come in close proximity to or engage each other while passing through the coating system such that, when the coating is applied over the parts and dried or cured, two or more parts may adhere together at the point of engagement (known as a “touch point”). These coated parts must then be separated from each other with some degree of force that, typically, results in the removal of at least some of the coating from the part at or around the touch point. Touch points are created also when a part touches the side of the conveyor. Additionally, even if no contact is made between objects or the sides of the conveyor, contact is still present between the object and the conveyor belt that it is resting on, and a touch point is created at each point of contact with the belt. At the very least, the touch point provides an unsightly blemish on the finished product. When the part is formed from a corrosive material, the touch point, in addition to its reduced appearance, has a substantially greater chance of developing premature signs of corrosion following assembly. Because the objects are randomly positioned on the belt, it is difficult to predict the location of the touch points prior to coating.
In some circumstances, due to aesthetic standards and/or quality requirements for the part, customers may require that certain areas of the part, such as the Class A surfaces, contain no touch points. For example, when the part is a bolt, it may be required that the Class A surfaces of the bolt, such as the head of the bolt, contain no touch points, while non-Class A surfaces, such as the shaft and threads of the bolt, may contain touch points.
In the random coating process described above, because the small parts move randomly on the conveyor belt, it has been difficult to control how and where touch points may occur, or to limit the touch points to non-Class A surfaces. Accordingly, in order to meet quality standards, the supplier employing this coating technique may find it necessary to incur time and cost consuming efforts to sort and scrap non-conforming parts.
In order to address some of the above-described problems in the prior art, it is known to provide a single-run, disposable belt that employs break-away pins that temporarily lock the small parts to the belt while the parts travel through the coating system. After the parts are coated and dried or cured, the parts are removed from the belt by snapping each part and the respective break-away pin from the belt. The used pins and belt are disposed of, and new pins and a new belt are employed for each subsequent coating run. Although this system provides some degree of consistency to the coating process, and controls, to some degree, the areas where the touch points appear, this system is relatively inefficient, in that it requires a high degree of operator maintenance for loading and unloading the belt, belt exchange, and waste management.
Accordingly, it would be a welcome addition in the art to provide an apparatus and process that can materially reduce or avoid the shortcomings in the prior art, improve coating efficiency, while providing a coated object that meets or exceeds stringent functional and aesthetic quality requirements.